1. Field of the Invention
This invention relates to liquid propellant guns utilizing a differential piston to provide continued or regenerative injection of the propellant into the combustion chamber after initial ignition, and more particularly to such guns having a balancing nozzle for recoilless operation.
2. Prior Art
Liquid propellant guns utilizing differential pistons to pump propellant into the combustion chamber during combustion are now well known. Early work is described in a Final Report of Nov. 19, 1953-Jan. 31, 1956 under contract DA-36-034-ORD-1504RD, Project TS1-47-8 by V. M. Barnes, Jr. et al which apparently in part corresponds to Jukes et al, U.S. Pat. No. 3,138,990 filed Oct. 9, 1961; in a report No. 17-2 of June 15, 1954 under contract NOrd-10448 by C. R. Foster et al; and in a Final Report of Sept. 1, 1957 under contract NOrd 16217, Task 1, by L. C. Elmore et al. Other patents of interest are J. W. Treat, Jr., U.S. Pat. No. 2,922,341, filed Nov. 7, 1955; E. J. Wilson, Jr., et al, U.S. Pat. No. 2,981,153, filed Nov. 14, 1952; C. M. Hudson, U.S. Pat. No. 2,986,072, filed Nov. 19, 1952; and E. J. Vass, et al, U.S. Pat. No. 3,690,255, filed Oct. 1, 1970.
Guns utilizing balancing nozzles to approximate recoilless operation are also now well known. Examples are: C. W. Musser, U.S. Pat. No. 2,924,149, filed Oct. 7, 1957; L. A. Skinner, U.S. Pat. No. 2,965,000, filed Dec. 20, 1960; R. G. Strickland et al, U.S. Pat. No. 3,129,636, filed Sep. 28, 1960; and A. J. Grandy, U.S. Pat. No. 3,338,133, filed Oct. 6, 1965. Musser and Grandy show the use of a frangible disk to close the balancing nozzle until pressure has built up in the combustion chamber. Strickland et al shows a plug attached to the projectile to restrict the balancing nozzle prior to translation of the projectile down the gun barrel. That is, to restrict the flow of exhaust combustion gas through the nozzle during the early phases of the combustion process in the recoilless gun. This restriction causes more rapid pressure buildup and higher acceleration for the projectile. However, the plug is attached to the projectile and this restriction it provides only occurs when the projectile is near the beginning of the gun barrel. Since the projectile has a very high initial acceleration, the plug is in the vicinity of the nozzle for only a very short initial period.
An object of this invention is to provide a recoilless gun wherein the rate of exhaust flow of the combustion gas through the balancing nozzle can be controlled over a major fraction of the combustion period, thereby to permit a more absolute balance of the forces of recoil and counterrecoil to provide a truly recoilless gun.
Another object of this invention is to provide a recoilless gun where the rate of exhaust flow of the combustion gas through the balancing nozzle can be controlled to reduce the blast field generated by the exhaust flow to a desired level. By blast field is meant the shock wave or waves generated in the volume or region of atmosphere surrounding the rear of the gun which is generated by the rapid introduction therein of the large volume of exhaust gas. Controlling the rate of introduction of this gas directly controls the strength of this shock wave and its overpressure.
A feature of this invention is the provision of a liquid propellant gun having a combustion gas responsive displacement mechanism to progressively inject propellant into a combustion chamber from a supply chamber, a gun barrel for the discharge of a projectile, a balancing nozzle for the discharge of combustion gas, and a plug coupled to said mechanism and serving to control the effective cross-section area of said nozzle in response to the displacement of said mechanism.